Why does it say "Aron Echad"?
Radak: It means Aron Ish Echad. 1
Malbim: This hints that there was another Aron elsewhere! Indeed, one of the 13 Shofaros (boxes) in the Mikdash in which people would put coins was for new Shekalim (of this year. Another was for old Shekalim, of previous years - refer to 12:10:4:1.) The Chataf Patach under the Aleph supports this 2 . Also 'Echad' hints to the 13 Shofaros; its Gematriya is 13.
Malbim: He infers so due to the Semichus, i.e. there is Chataf Patach under the Aleph. (If it were not Samuch, it should be a Kamatz, like we find regarding 'Adon' - PF.) His Perush is difficult. Meshech Chachmah (Haftoras Parshas Shekalim) - they took an individual's Aron, lest it be Batel to the building, and they transgress adding to the Mikdash. (It says "Aron Echad" also in Divrei ha'Yamim II, 24:8, and there it says that it was outside Sha'ar Beis Hashem! Perhaps it was the same Aron; they moved it from one place to another. (PF)
I.e. it is Samuch to Echad. Perhaps Malbim explains that it is as if it says Aron ha'Echad (Samuch). (PF)
Why did they make a hole in the door of the Aron?
'Rashi' (Divrei ha'Yamim II, 24:8): This enabled people to cast coins inside. They did not want to open the door, lest a swindler steal from it.
What is the meaning of "mi'Yamin b'Vo Ish"?
Rashi: It is to the right of where people enter.
What are "Shomerei ha'Saf"?
Rashi: They guard Safei (the gates of) ha'Azarah; they are appointed over the keys of the Azarah. Yonason translates Amarkelaya 1 . There were seven Amarkelim, for the seven gates of the Azarah (Tosefta Shekalim 2:15).
Radak: They guard Klei ha'Bayis. Saf is a general term for Klei Shares.
Radak: This is a great Gizbar (overseer of Hekdesh) appointed over others. Targum Onkelos of "v'Nasi Nesi'ei ha'Levi" (Bamidbar 3:32) is 'Amarkelaya d'Memana Al Ravrevei Livai.'
Here it says that the box was put by the Mizbe'ach. Divrei ha'Yamim II, 24:8 says that they put it in the gate, outside!
Malbim: They put a box by the Mizbe'ach to collect Shekalim for this year. They put another box in the gate, outside, for extra Shekalim to compensate for previous years [refer to 12:5:3:1 and the note there).
